This derailleur, which I have been told is called the ‘Altenburger Champion’, was designed as a racing gear. This was unusual for a derailleur that mounted under the chainstay - a position generally reserved for touring equipment. On a number of occasions during the 1950’s, the Altenburger Champion was used by the German team in the Tour de France.
I have also been told that this model had a less deluxe sibling that was called the Altenburger Tourist (represented here as a GB Altenburger). I am slightly dubious about this theory - there seem to be too few differences between the two to justify providing the choice. My personal view is that this version (with two stops) is an later variant, and the other version (with one stop) is an earlier variant.
Compared to the pull-chain derailleurs of the time, the Altenburger Champion is a precise, rigid, parallelogram design. Compared to the Campagnolo Gran Sport it is extremely light and makes extensive use of aluminium.
For some reason Altenburger did not push sales of this derailleur, preferring to concentrate on their very successful brakes. Nevertheless, it is a sophisticated piece of equipment for its time.